Percentage Calculator - Free Online Tool

Calculate percentages, percentage increase/decrease, and find what percentage one number is of another

Percentages are one of the most common mathematical concepts used in everyday life, from calculating discounts during shopping to determining tax amounts, interest rates, and statistics. Our free percentage calculator helps you quickly and accurately calculate percentages, percentage increases, percentage decreases, and percentage changes. Whether you're a student working on homework, a professional analyzing business metrics, a shopper comparing prices, or anyone who needs to work with percentages, this tool simplifies complex percentage calculations into easy-to-understand results. The calculator supports multiple calculation types including finding what percent one number is of another, calculating percentage increase or decrease, determining the percentage change between two values, finding what percentage a part is of a total, and reverse-calculating the original whole from a known percentage. With instant results, step-by-step explanations, visual charts, scenario comparison, and export capabilities, you'll not only get the answer you need but also understand how the calculation works. No registration required, completely free to use, and works perfectly on all devices including smartphones, tablets, and desktop computers.

Understanding Percentage Calculations

A percentage is a way of expressing a number as a fraction of 100. The word 'percent' literally means 'per hundred,' making percentages a universal way to compare proportions and ratios. Understanding how to calculate percentages is essential for many real-world applications.

What is a Percentage?

A percentage represents a portion of a whole, where the whole is always considered to be 100. For example, 50% means 50 out of 100, which is the same as one-half or 0.5 as a decimal. Percentages make it easy to compare different quantities on a common scale. When you see that a product is 25% off, you immediately understand that you'll save one-quarter of the original price without needing to know the exact dollar amount.

How to Calculate X% of Y

To find what percent X is of Y, use the formula: (X ÷ Y) × 100. For example, to find what 25 is as a percentage of 200, divide 25 by 200 to get 0.125, then multiply by 100 to get 12.5%. Alternatively, to find X% of a number Y, multiply Y by X and divide by 100. For instance, 20% of 150 is (150 × 20) ÷ 100 = 30. This calculation is commonly used for calculating discounts, tips, taxes, and commissions.

Percentage Increase and Decrease

Percentage increase shows how much a value has grown relative to its original amount. To calculate, find the difference between new and old values, divide by the old value, and multiply by 100: ((New - Old) ÷ Old) × 100. For example, if a stock price increases from $50 to $60, the percentage increase is ((60 - 50) ÷ 50) × 100 = 20%. Percentage decrease works the same way but results in a negative number. It's important to note that percentage increases and decreases are not symmetric – a 50% decrease followed by a 50% increase does not return you to the original value.

Common Percentage Mistakes to Avoid

One common mistake is confusing percentage points with percentages. If interest rates increase from 3% to 5%, that's a 2 percentage point increase, but a 66.7% relative increase. Another mistake is assuming that percentage increases and decreases are reversible – if a value decreases by 20%, you need a 25% increase to return to the original value, not 20%. Always ensure you're using the correct base value when calculating percentages, as using the wrong reference point will give you incorrect results.

Percentage Formulas

Percentage of a Number

Result = (P / 100) × N

Finds P percent of a number N. Convert the percentage to a decimal by dividing by 100, then multiply by the base number.

Percentage Change

% Change = ((New − Old) / Old) × 100

Measures the relative change between two values. A positive result indicates an increase; a negative result indicates a decrease.

Percentage Difference

% Difference = |A − B| / ((A + B) / 2) × 100

Calculates the relative difference between two values using their average as the reference point, useful when neither value is the clear baseline.

Finding the Whole from a Percentage

Whole = Part / (P / 100)

Reverse-calculates the original total when you know a part value and the percentage it represents.

Common Percentage Equivalents

Percentage, Fraction, and Decimal Equivalents

Quick reference table showing common percentage values with their fraction and decimal equivalents.

Percentage	Fraction	Decimal
1%	1/100	0.01
5%	1/20	0.05
10%	1/10	0.10
12.5%	1/8	0.125
20%	1/5	0.20
25%	1/4	0.25
33.33%	1/3	0.3333
40%	2/5	0.40
50%	1/2	0.50
60%	3/5	0.60
66.67%	2/3	0.6667
75%	3/4	0.75
80%	4/5	0.80
90%	9/10	0.90
100%	1/1	1.00

Worked Examples

Find 15% of 240

You need to calculate 15% of 240 — for example, a 15% tip on a $240 bill.

Convert 15% to a decimal: 15 / 100 = 0.15

Multiply by the base number: 0.15 × 240 = 36

15% of 240 is 36.

Calculate the Percentage Change from 80 to 96

A product's price increased from $80 to $96. What is the percentage change?

Find the difference: 96 − 80 = 16

Divide by the original value: 16 / 80 = 0.20

Multiply by 100: 0.20 × 100 = 20%

The price increased by 20%.

Find What Percentage 45 Is of 180

You scored 45 out of 180 points on a test. What percentage is that?

Divide the part by the total: 45 / 180 = 0.25

Multiply by 100: 0.25 × 100 = 25%

45 is 25% of 180.

How to Use

Select calculation type

Choose from six percentage calculation modes: find X% of Y, increase or decrease a value by a percentage, calculate percentage change between two values, find what percentage one number is of another, or reverse-calculate the whole from a known percentage.

Enter values

Input the required numbers for your chosen calculation. The fields change dynamically based on the calculation type you select. For basic percentage calculations, enter the base value and percentage. For percentage change, enter the original and new values.

Review results and steps

See the calculated result instantly along with a detailed step-by-step breakdown showing exactly how the answer was derived. A visual donut chart illustrates the proportional relationship between the values.

Compare and export

Use the comparison mode to evaluate multiple percentage scenarios side by side with visual bar charts. Export your calculations to CSV for spreadsheets, or print the results directly from your browser. Your calculation history is saved for the session.

Frequently Asked Questions

How do I calculate X% of Y?

To find what percentage X is of Y, divide X by Y and multiply by 100. The formula is: (X ÷ Y) × 100 = Percentage. For example, to find what percentage 30 is of 150, calculate (30 ÷ 150) × 100 = 20%. This calculation is useful when you want to express one quantity as a percentage of another, such as determining what percentage of your monthly income goes to rent, or what percentage of exam questions you answered correctly. The result tells you the relative proportion of X compared to the total Y. Remember that X should be less than or equal to Y when finding a percentage of a whole, though percentages can exceed 100% when comparing quantities where one is larger than the other.

How do I calculate percentage increase?

Percentage increase measures the relative change between two values, while percentage points measure the absolute difference between two percentages. For example, if unemployment rises from 5% to 8%, that's an increase of 3 percentage points but a 60% percentage increase ((8-5)÷5×100). Percentage points are used when discussing changes in rates, proportions, or percentages themselves. In financial contexts, this distinction is crucial: if your interest rate increases from 2% to 3%, that's 1 percentage point or a 50% increase in the rate. Media often confuses these terms, so understanding the difference helps you interpret statistics correctly. When comparing percentages, use percentage points; when measuring growth or decline, use percentage change. This distinction becomes especially important in fields like economics, finance, and statistics where precision matters.

How do I calculate percentage decrease?

Percentage change is calculated using the formula: ((New Value - Old Value) ÷ Old Value) × 100. For example, if a product's price changes from $80 to $100, the percentage change is ((100 - 80) ÷ 80) × 100 = 25% increase. If the price drops from $100 to $80, it's ((80 - 100) ÷ 100) × 100 = -20% decrease. Notice that the percentage increase and decrease are different even though the absolute change ($20) is the same – this is because they use different base values. The old value is always your denominator in the formula. Percentage change is widely used in finance to track stock prices, in business to measure sales growth, in economics to monitor inflation, and in science to quantify experimental changes. A positive result indicates an increase, while a negative result indicates a decrease.

How do I find percentage change?

This common misconception occurs because percentage changes use different base values. Starting with 100, a 50% decrease gives you 50 (100 - 50% of 100). But a 50% increase from 50 only adds 25 (50% of 50), bringing you to 75, not back to 100. To return to the original value after a 50% decrease, you need a 100% increase. Similarly, after a 50% increase to 150, you need only a 33.3% decrease to return to 100. This asymmetry exists because the base value changes after the first calculation. This principle is important in investing: if your portfolio drops 50%, it needs a 100% gain to recover. Understanding this helps explain why market recoveries often seem slower than declines. In practical terms, always calculate each percentage change based on its current starting value, not the original value, unless you're calculating cumulative percentage change from a fixed baseline.

What is a reverse percentage calculation?

A reverse percentage calculation lets you find the original whole when you know a part and the percentage it represents. For example, if you know that $75 is 25% of some total, you can find the total by dividing 75 by 0.25, which gives $300. This is commonly needed in real-world situations: if a discounted item costs $60 after a 20% discount, the original price was $60 ÷ 0.80 = $75. Similarly, if sales tax of $8.50 represents 8.5% of a purchase, the pre-tax price was $8.50 ÷ 0.085 = $100. The formula is: Whole = Known Value ÷ (Known Percentage ÷ 100). This calculation is essential for accountants working backward from tax amounts, shoppers figuring out original prices before discounts, and analysts reconstructing base figures from reported percentages.

How does the comparison mode work?

The comparison mode lets you evaluate multiple percentage scenarios side by side. Click the Compare Scenarios button to open the comparison panel, where you can add rows with different percentage and value combinations. Each row shows the calculated result and a visual bar chart for quick comparison. This is particularly useful when shopping and comparing discounts across stores, evaluating different tip percentages at a restaurant, comparing interest rate impacts on loans, or analyzing how different growth rates affect business projections. You can add as many scenarios as you need and remove any that are no longer relevant. The bar charts scale relative to the largest result, making it easy to see proportional differences at a glance.